The step height of stair-type seawalls is typically set between 0.2 to 0.3 m. These short-rise stair-type seawalls have a gradual slope that creates aesthetic problems, such as an increase in the construction area, as well as functional problems, such as an increase in the wave run-up. To solve these problems, this study recommends that the step height be increased to 1.0 - 1.4 m. Numerical calculations using CADMAS-SURF clearly identify the characteristics of the dimensionless run-up height and wave reflection coefficient for varying cases with step heights between 0.2 m and 1.4 m. The validity of the numerical simulations is compared to experimental results on smooth slopes by Savage and Greslou-Mahe. The dimensionless run-up height and wave reflection coefficient are unified by the surf similarity parameter. It is demonstrated that increasing the step height generally reduces these parameters and that there is an increase in reflection coefficient for the gradual slope conditions. These parameters are also associated with wave-breaking morphology, step steepness, and the reflection from the step surface.